CST2 and Parkinson disease: Cystatin SA, A, A N-acetylated, B-SSC, B S-S dimer, statherin des F43, secretory leukocyte proteinase, thymosin β4, S100A9s were significantly increased, whereas histatin 1, statherin 1P, 2P, desD1, des1-9, des1-10, proline-rich protein (PRP) 0P, 3P, and cystatin SN were significantly decreased in the PD group.